1. Field of the Invention
The present invention relates generally to display devices and, more particularly, to an electronic display formed of an array of optically variable indicators portraying the value of two or more measured parameters relative to a fixed scale or to each other.
2. Description of the Prior Art
Meters, mechanical pointers, dial displays, and similar display arrangements used to reflect a measured parameters have long been known. In the past, and to a great extent continuing to the present, most such display or indicator devices were mechanical in nature and included one or more pointers or dials to register the value of the measured input. With the development of light emitting diodes, liquid crystal display elements, and the like, digital format electronic displays are available and compatibly form total electronic measuring and indicating assemblies having no moving parts.
The above displays provide a digital readout, thus, are primarily useful for applications where precision and accuracy in the readout of the measured parameter are required. In many instances, however, an analog output is preferred. In those situations, even though the driving circuits may be produced using sophisticated integrated circuit techniques, the actual display elements typically remain mechanical in nature with the result that the overall system suffers from all of the inaccuracies and limitations inherent in such mechanical assemblies.
Following the pattern of development of the general display art, is the development of solid state, electronic watches and other horological instruments for the display of time. In such cases, the segmented digital display is popularly employed in place of conventional mechanical hands; however, this practice requires the watch bearer to learn to accept a new format for the presentation of the current time as well as the passage of time. On the other hand, the conventional analog presentation permits the watch owner to automatically conceptualize furture or past time by direct visual comprehension without having to make a mental arithmetic computation as is the case with digital format.
Thus, while the total electronic driving circuit is preferred in watches and other indicators because of its inherent accuracy and small size, the conventional mechanical analog presentation is also preferred because of the enhanced visual comprehension provided by such a readout as compared with the digital format. In the past, this preference has required that electrical output signals be converted into mechanical movements of the pointers of the short and long hands, resulting in a complicated structure necessitating a direct electrical-mechanical interface with associated disadvantages. Consequently, considerable design effort has been spent in an attempt to develop a total electronic display having an analog readout.
The prior art, as exemplified by U.S. Pat. Nos. 3,275,871 and 3,833,933, is generally cognizant of solid state display assemblies which attempt to simulate the movement of a mechanical pointer. In addition, U.S. Pat. Nos. 3,276,200, 3,540,209, 3,823,549, 3,844,105, and 3,908,355, represent a number of prior art attempts to incorporate total electronic analog indicators in a timekeeping instrument. White these devices have obviated the necessity for mechanical pointers or hands, they have not proven to be totally satisfactory in that the display does not fully simulate the appearance of the more familiar mechanical pointer or hands and involves considerable complexity in attempting to facilitate the measurement of two or more indendent parameters.